Cost reduction, miniaturization, inspection time reduction, simplicity of operation, and the like are required for diagnostic equipment for a human body used at home, a simple diagnostic facility or the like. A sensor IC (integrated circuit: semiconductor integrated circuit) formed on a semiconductor integrated circuit can satisfy such a requirement.
For example, an example of a sensor IC formed on a semiconductor integrated circuit is disclosed in PTL 1. FIGS. 7 to 9 are diagrams for explaining the sensor IC according to PTL 1.
FIG. 7(a) is a diagram illustrating a circuit configuration of the sensor IC. As illustrated in FIG. 7(a), the sensor IC includes oscillators 110 and 120 having inductors 111 and 121 formed on a metal layer (metal layer) on a semiconductor substrate 101. FIG. 7(b) is a diagram illustrating an example in which the circuit illustrated in FIG. 7(a) is mounted on the semiconductor substrate 101. As illustrated in FIG. 7(b), the oscillators 110 and 120 are provided in a row. For the simplicity, transistors, capacitors, and the like are represented as other circuits 112 and 122.
FIG. 8(a) is a diagram illustrating a state in which a magnetic particle 113 and an inspection target 114 are brought into contact with the inductor 111. As illustrated in FIG. 8(a), when the inspection target 114 is brought into contact with the semiconductor substrate 101 illustrated in FIG. 7(b), a magnetic permeability changes due to the fluctuation of the magnetic particle 113 attached to the inspection target 114, and inductances of the inductors 111 and 121 are affected by the change of the magnetic permeability. As a result, the oscillation frequencies output by the oscillators 110 and 120 change, and a detector (not illustrated) detects the change in the oscillation frequency. The change in the oscillation frequency indicates the variation in the properties of the inspection target 114.
For example, the oscillator 110 is to be used as a sensor portion among the oscillators 110 and 120, and thus, the inspection target 114 is selectively brought into contact with the oscillator 110. FIG. 8(b) is a diagram illustrating a state in which an inspection target 124 is further brought into contact with the inductor 121 comparing with the state illustrated in FIG. 8(a). The other oscillator 120 is to be used as a reference portion, and thus, the other oscillator 120 may not be brought into contact with the inspection target or may be brought into contact with the inspection target 124 used as a reference as illustrated in FIG. 8(b). In this way, the property difference of the inspection target 114 can be evaluated by checking a difference in the oscillation frequencies of the oscillators 110 and 120 using an enable signal or a /enable signal.
FIG. 9(a) is a view illustrating a position of a cross section A-A′ of the semiconductor substrate 101. FIG. 9(b) is a cross-sectional view illustrating the cross section A-A′ of the semiconductor substrate 101. As illustrated in FIG. 9(b), even if the inductor 111 formed on the metal layer formed on the highest metal layer 130 in the semiconductor substrate 101, since a protection film 115 formed of an insulator or the like is formed between the surface of the semiconductor substrate 101 and the inductor 111, the inspection target 114 does not come in contact with the highest metal layer 130. The above description is similarly applicable to the inductor 121.
However, in the sensor IC disclosed in PTL 1 and NPL 1, it is necessary to connect the magnetic particle 113 to the inspection target 114 which is brought into contact with the semiconductor substrate 101. According to NPL 1, the frequency variation due to the variation of the magnetic particle 113 is proportional to the magnetic susceptibility χ. The magnetic susceptibility χ is a ratio of H to the magnetic polarization Pm generated in the magnetic material when the external magnetic field H is applied. As illustrated in FIG. 16.8.1, the magnetic particle in NPL 1 becomes positive at a frequency lower than 2 GHz, and the magnetic polarization becomes opposite to the external magnetic field. Furthermore, in the figure, there is almost no variation at higher frequencies such as exceeding 10 GHz.